Acta Crystallographica Section B

Structural Science, Crystal Engineering and Materials

Volume 69, Part 2 (April 2013)

research papers

Acta Cryst. (2013). B69, 214-227    [ doi:10.1107/S2052519213001772 ]

A highly hydrated [alpha]-cyclodextrin/1-undecanol inclusion complex: crystal structure and hydrogen-bond network from high-resolution neutron diffraction at 20 K

D. Gallois-Montbrun, G. Le Bas, S. A. Mason, T. Prangé and S. Lesieur

Abstract: The monoclinic C2 crystal structure of an [alpha]-cyclodextrin/1-undecanol host-guest inclusion complex was solved using single-crystal neutron diffraction. Large high-quality crystals were specially produced by optimizing temperature-controlled growth conditions. The hydrate crystallizes in a channel-type structure formed by head-to-head dimer units of [alpha]-cyclodextrin molecules stacked like coins in a roll. The alkyl chain of the guest lipid is entirely embedded inside the tubular cavity delimited by the [alpha]-cyclodextrin dimer and adopts an all-trans planar zigzag conformation, while the alcohol polar head group is outside close to the [alpha]-cyclodextrin primary hydroxyl groups. The cyclodextrin dimer forms columns, which adopt a quasi-square arrangement much less compact than the quasi-hexagonal close packing already observed in the less hydrated [alpha]-cyclodextrin channel-type structures usually found with similar linear guests. The lack of compactness of this crystal form is related to the high number of interstitial water molecules. The replacement of 1-undecanol by 1-decanol does not modify the overall crystal structure of the hydrate as shown by additional X-ray diffraction investigations comparing the two host-guest assemblies. This is the first study that analyses the entire hydrogen-bonding network involved in the formation of a cyclodextrin dimer surrounded by its shell of water molecules.

Keywords: cyclodextrin dimer; monoalkyl lipid; channel assembly; host-guest inclusion compound; hydrogen bonding; single-crystal neutron diffraction.

hkldisplay filedownload file

Structure factor file (CIF format) (635.6 kbytes)
[ doi:10.1107/S2052519213001772/eb5023C11neutronsup2.hkl ]
Contains datablock C11neutron

hkldisplay filedownload file

Structure factor file (CIF format) (290.8 kbytes)
[ doi:10.1107/S2052519213001772/eb5023c11Xraysup3.hkl ]
Contains datablock c11Xray

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Structure factor file (CIF format) (281.7 kbytes)
[ doi:10.1107/S2052519213001772/eb5023c10Xraysup4.hkl ]
Contains datablock c10Xray


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